1. Field of the Invention
The present invention relates to a sewing machine.
2. Description of the Prior Art
When threading the needle thread pulled out from a spool on a sewing machine, the needle thread is passed sequentially through a thread guard, a thread guide, a needle thread tension regulator, a thread takeup device and the eye of a needle. When changing the needle thread, the spool is replaced with another spool and the needle thread pulled out from another spool is threaded on the sewing machine, or the needle thread of the old spool is cut at a position near the spool, the free end of the needle thread of another spool and the trailing end of the needle thread threaded on the sewing machine are tied up and the needle thread extended through the eye of the needle is pulled to thread the needle thread of another spool on the sewing machine.
However, whichever threading methods may be used, the change of the needle thread takes time and the tension of the needle thread must be adjusted every time the needle thread is changed, which also takes time.
Incidentally, a sewing machine disclosed in U.S. Pat. No. 4,590,875 is provided with a sewing head provided with a needle bar, and capable of being removed from the arm and of being replaced with another sewing head provided with a needle bar according to desired stitching operation, such as lock stitching operation or zigzag stitching operation. However, since the spool pin, the needle thread tension regulator and the yarn guides and the like of this sewing machine are arranged on the arm, the needle thread needs to be threaded on the sewing machine when the sewing head is changed.